1. Technical Field
The present disclosure relates to an illuminating device, and in particular relates to an illuminating device providing uniform illumination.
2. Related Art
FIG. 1 shows a conventional illuminating device 1, which is disposed on a supporting plate 2. The illuminating device 1 emits light beam 4 toward the ceiling 3. The light beam 4 is reflected by the ceiling 3, and scattered downward to provide illumination.
Conventionally, the light beam 4 is reflected centrally by an area A of the ceiling 3. The brightness contrast between the area A and an area B of the ceiling 3 is thus strong. The high brightness contrast provides discomfort to users, wherein users may feel illumination is insufficient. The distribution of brightness on a ceiling may be used to define indoor illumination uniformity. Conventionally, a min/avg brightness uniformity ratio of a ceiling is about 0.34, and a min/max brightness uniformity ratio of a ceiling is about 0.06.